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The brown recluse spider (Loxosceles reclusa) is a small arachnid with great potential to inflict physical harm. More potent than a rattlesnake’s venom, the toxin emitted by the brown recluse has the ability to rupture cell membranes and destroy regional nerves, blood vessels, and fatty tissue. Envenomation by the brown recluse can lead to severe necrosis of the cutaneous tissues.1,2
In the United States, L reclusa is one of 13 species of Loxosceles—five of which have been associated with necrotic lesions resulting from bites and envenomation.3 Though rare, and virtually nonexistent across significant portions of North America,4 the brown recluse is often cited as the offending creature in reported bites involving envenomation5 (with reports sometimes outnumbering estimated numbers of specimens in a given area6). Considering the limited range within which the spider is considered endemic, any patient who presents reporting a possible brown recluse spider bite (or who presents with a wound suspected of being such a bite) must be questioned quickly and carefully. The first and foremost question: where, geographically, was the patient bitten?
Endemic Areas
Brown recluse spiders are known to be present in the subtropical areas of North America—but not in areas with high humidity. According to arachnologists in the southeastern United States, the closer one is to the Gulf of Mexico, the less likely one is to encounter a brown recluse.7 This spider is most commonly found in eastern Texas, Arkansas, areas west of the Appalachian Mountains, and northern areas of the Gulf Coast states (see Figure 18). They are virtually nonexistent along the Atlantic seaboard and the Gulf Coast,4 although lone specimens of Loxosceles species have been reported in numerous nonendemic areas, suggesting possible transport through commerce or family relocation.9 One suspected case of brown recluse envenomation was recently reported in New York State.10
If it is determined that the geographic area in question is indeed populated by brown recluse spiders, more detailed history must then be elicited from the patient regarding recent activities. The brown recluse may reside indoors and often hides in bed sheets, blankets, and stored clothing. This spider also may be found behind furniture, in basements and cupboards, or in other small, tight areas. It is commonly found in cardboard boxes stored in a closet or an attic,11 and boxes with folded flaps are a preferred dwelling place.7 (Thus, a remote chance that L reclusa can be inadvertently transported to a nonendemic area9 does exist.)
In the outdoors, the brown recluse may be found in woodpiles, piles of leaves or other natural debris, in outdoor sheds or garages, under rocks, and in other places that are relatively dark and seldom used.12
Patient Presentation/Patient History
Initially, patients with a brown recluse spider bite may present to a primary care provider with complaints of mild pain and itching, presumably around the bite site. Within eight hours, the pain becomes stabbing and penetrating and may give way to a burning sensation.7
Patients with a positive pertinent history who are at increased risk for a bite are those who live in areas where these spiders are endemic and who have been performing tasks in areas where these spiders might reside. Not wearing long pants and long-sleeved shirts contributes to the probability that a patient has sustained a bite.
Physical Examination
The site of the suspected bite and surrounding skin should be examined carefully. A pustule, generally small and white, may appear, surrounded by erythema. For as long as 24 hours following the time of the initial bite, a volcano-like lesion may be present, with a sunken central “crater” that has raised edges. While the center of the lesion is free of inflammation, the surrounding skin is typically red and inflamed.12
Pathologically, a specified sequence occurs following a bite with envenomation. Initially, platelets aggregate, followed by endothelial swelling and destruction (see Figure 2a). Gradually, this leads to the blocking of capillaries with white blood cells, which results in ischemia and ultimately necrosis.1
The clinical manifestations of the brown recluse spider bite may vary, based on the amount of venom injected and the age and overall health of the patient. One who has been bitten with minimal envenomation may experience little more than mild erythema, localized urticaria, and generalized discomfort that resolves spontaneously in three to five days.1
In patients who experience more significant envenomation, a “bull’s-eye” lesion may appear. The center of the wound may be bluish in hue, with concentric rings—an inner pale ring, and an outer reddened ring. The center of the wound subsequently forms a hemorrhagic bleb that will typically become necrotic. Eventually, as the eschar matures, the necrotic tissue will slough off, and an area of granulation will develop. Full healing of the wound may take from four weeks to as long as six months.1
Laboratory Workup
A complete blood count, including platelet count and differential, will allow the provider to observe for disseminated intravascular coagulation, hemolysis, and thrombocytopenia. The abnormal results most commonly found in patients who have sustained a brown recluse spider bite are leukocytosis and an elevated erythrocyte sedimentation rate. A skin biopsy of the site may reveal the presence of eosinophils, neutrophils, and thrombosis, all of which support the diagnosis of a brown recluse spider bite.2
A valid, reliable test to detect Loxosceles venom is needed in the clinical setting; the differential diagnosis for brown recluse spider bites is broad (see the table1,6,11,13-15 below), and diagnostic error can occur, delaying appropriate treatment for the actual presenting condition—which could be debilitating or in rare cases, fatal.16 One test for Loxosceles venom, though not currently marketed for use in humans, shows potential. It is a polyclonal enzyme-linked immunosorbent assay (ELISA) with a demonstrated ability to detect venom in rabbits for as long as seven days after injection.7 Further refinement of the polyclonal ELISA is under way in efforts to increase its sensitivity and specificity.17
Diagnosis
Diagnosis of a brown recluse spider bite is difficult at best. Other potential causes of the associated presenting symptoms should be excluded before a brown recluse spider bite is considered confirmed.
Several factors add to the difficulty of diagnosing a brown recluse bite. Oftentimes it may take the patients days or weeks after the bite to see a health care provider, and they rarely present with the spider that bit them (or that they believe bit them).1 Currently, the only true standard for proof of envenomation by a brown recluse is to collect the spider and have its identify verified by an entomologist or other expert—not necessarily the health care provider.
One condition that is frequently misdiagnosed as a brown recluse bite is methicillin-resistant Staphylococcus aureus infection (MRSA; see Figure 2b). Misdiagnosis as a bite will delay appropriate treatment for MRSA and possibly lead to transmission of infection to others, as the unaware patient does not take proper precautions to avoid spreading MRSA to others.7 Patients with MRSA who experience significant tissue eradication or tissue death, or who have developed systemic symptoms, are candidates for hospitalization and possibly surgical debridement.2
Treatment/Management
Even without proper verification that the lesion is the bite of a brown recluse, it remains essential to provide basic treatment—initially, to wash the area with mild soap and water, then elevate the affected extremity and apply ice; rest is recommended.12 The patient’s tetanus immunization status should be verified, with tetanus vaccine administered if appropriate.7,11
While most brown recluse bites will resolve without major treatment within two to three months, disabling manifestations warrant treatment. Treatment goals are to keep the skin intact, decrease the likelihood that infection will spread, and maintain circulation to the affected area.
Several treatment options are possible for a confirmed brown recluse spider bite with envenomation. Oral dapsone, initiated within 36 hours, has been shown to reduce or delay the need for surgical intervention in cases of severe necrotic arachnidism.2,13,18,19 Dosage ranges from 50 mg/d to 100 mg/d, divided bid for adults; and for children, 1.0 to 2.0 mg/kg/d, not to exceed 100 mg/d.3
Before dapsone is prescribed or administered, the patient must be tested for glucose-6-phosphate dehydrogenase (G6PD) deficiency, as dapsone use in such individuals can lead to hemolysis.3,20 Clinicians unfamiliar with this medication should request a consultation with an expert (eg, in infectious disease, wound care, pharmacology) regarding treatment and the need for monitoring potential adverse effects. Additionally, although dapsone has been recommended for this indication for longer than 20 years, few human studies have been reported to support its use.19
The anti-inflammatory effects of steroids may be useful in some cases, as they may provide red blood cell membrane–stabilizing effects in patients with systemic loxoscelism.7 Although no guideline currently exists for dosing of glucocorticoids in spider bite treatment, a shorter period of eschar duration was reported in one animal study involving methylprednisolone administered within two hours of inoculation, dosed at 2 mg/kg of body weight initially, then daily for two days longer.11
Antibiotics may minimize the inflammatory reaction at the bite site, although generally, antibiotics are reserved for infections and not recommended for prophylaxis. Antihistamines may be used to relieve minor symptoms related to histamine release (eg, itching) and also for treatment of anaphylaxis.3 Analgesics, such as acetaminophen, may be prescribed for minor discomfort. Clinicians should individualize medication use (both drug and dose) based on the needs of the patient.
Hyperbaric oxygen therapy, a modality commonly used in wound healing, has been theorized to break down sphingomyelinase-D, thus preventing further spread of venom.1,21 In patients treated with this modality for brown recluse bites, reported results have been mixed.7
Follow-Up
Daily wound checks should be performed until the lesion is noted to be improving or no longer worsening. At each follow-up for the initial 72 hours, it is recommended that patients undergo a CBC, including platelet level, to detect progression of the infection or systemic involvement, and urinalysis to check for hematuria. Renal function should be monitored as needed.1,2
Patient Education
Regarding brown recluse spider bites, patients should be advised to keep five points in mind:
• Diagnosis is made by confirmation that the spider is a brown recluse, ideally with the capture and expert evaluation of the spider22
• Workup will focus on history, geographic locale, and environ of patient when supposed bite occurred4,7,8
• Treatment varies but may include a tetanus shot, antibiotics, dapsone, steroids, hyperbaric oxygen therapy, and in severe cases of necrosis, surgery1,2,7,19,20
• Follow-up will occur routinely during the initial 72 hours1,2
• Prevention of bites includes avoiding piles of clutter in garages, sheds, and under beds; and wearing long sleeves when working in these areas.12
Finally, because the venom of the brown recluse spider is poisonous, the NIH encourages exposed persons to contact the National Poison Control Center at (800) 222-1222.23
Conclusion
Brown recluse spider bites, though most likely overdiagnosed, do occasionally occur in areas where the creature is endemic. However, a brown recluse spider bite should be considered a diagnosis of exclusion and other possibilities considered first in light of their limited presence in North America and their nonaggressive nature.
Any patient who calls to report a suspected brown recluse spider bite should be instructed to bring the spider to the office, if possible, for identification. The spider should then be identified with certainty as a brown recluse by the appropriate expert so that treatment for the patient can be based on a correct diagnosis rather than one of presumption.
1. Wilson JR, Hagood CO Jr, Prather ID. Brown recluse spider bites: a complex problem wound. A brief review and case study. Ostomy Wound Manage. 2005;51(3):59-66.
2. Rhoads J. Epidemiology of the brown recluse spider bite. J Am Acad Nurse Pract. 2007; 19(2):79-85.
3. Arnold TC. Spider envenomation, brown recluse. http://emedicine.medscape.com/article/772295-overview. Accessed November 23, 2010.
4. Vetter RS, Hinkle NC, Ames LM. Distribution of the brown recluse spider (Araneae: Sicariidae) in Georgia with comparison to poison center reports of envenomations. J Med Entomol. 2009;46(1):15-20.
5. Pagac BB, Reiland RW, Bolesh DT, Swanson DL. Skin lesions in barracks: consider community-acquired methicillin-resistant Staphylococcus aureus infection instead of spider bites. Mil Med. 2006;171(9):830-832.
6. Frithsen IL, Vetter RS, Stocks IC. Reports of envenomation by brown recluse spiders exceed verified specimens of Loxosceles spiders in South Carolina. J Am Board Fam Med. 2007;20(5):483-488.
7. Swanson DL, Vetter RS. Loxoscelism. Clin Dermatol. 2006;24(3):213-221.
8. CDC. Necrotic arachnidism: Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep. 1996;45(21):433-436.
9. Gertsch WJ, Ennik F. The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bull Am Museum of Nat Hist. 1983;175:265-360.
10. Andersen RJ, Campoli J, Johar SK, et al. Suspected brown recluse envenomation: a case report and review of different treatment modalities. J Emerg Med. 2010 Apr 2. [Epub ahead of print]
11. Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med. 2005;352(7):700-709.
12. Nunnelee JD. Brown recluse spider bites: a case report. J Perianesth Nurs. 2006;21(1):12-15.
13. Naidu DK, Ghurani R, Salas RE, et al. Osteomyelitis of the mandibular symphysis caused by brown recluse spider bite. Eplasty. 2008 Aug 28;8:428-433.
14. Osterhoudt KC, Zaoutis T, Zorc JJ. Lyme disease masquerading as brown recluse spider bite. Ann Emerg Med. 2002;39(5):558-561.
15. Russell FE, Gertsch WJ. For those who treat spider or suspected spider bites. Toxicon. 1983;21(3):337-339.
16. Vetter RS, Bush SP. Reports of presumptive brown recluse spider bites reinforce improbably diagnosis in regions of North America where the spider is not endemic. Clin Infect Dis. 2002;35(4):442-445.
17. McGlasson DL, Green JA, Stoecker WV, et al. Duration of Loxosceles reclusa venom detection by ELISA from swabs. Clin Lab Sci. 2009;22(4):216-222.
18. Wendell RP. Brown recluse spiders: a review to help guide physicians in non-endemic areas. South Med J. 2003;96(5):486–90.
19. Rees RS, Altenbern DP, Lynch JB, King LE Jr. Brown recluse spider bites: a comparison of early surgical excision versus dapsone and delayed surgical excision. Ann Surg. 1985;202 (5):659-663.
20. Webster GF. Is topical dapsone safe in glucose-6-phosphate dehydrogenase-deficient and sulfonamide-allergic patients? J Drugs Dermatol. 2010;9(5):532-536.
21. Merchant ML, Hinton JF, Geren CR. Effect of hyperbaric oxygen on sphingomyelinase D activity of brown recluse spider (Loxosceles reclusa) venom as studied by 31P nuclear magnetic resonance spectroscopy. Am J Trop Med Hyg. 1997;56(3):335-338.
22. Bennett RG, Vetter RS. An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse or hobo spider bites in Canada. Can Fam Physician. 2004;50:1098-1101.
23. MedlinePlus, US National Library of Medicine, NIH. Brown recluse spider. www.mdconsult.com/das/patient/body/225048384-2/0/10041/32560.html. Accessed November 23, 2010.
The brown recluse spider (Loxosceles reclusa) is a small arachnid with great potential to inflict physical harm. More potent than a rattlesnake’s venom, the toxin emitted by the brown recluse has the ability to rupture cell membranes and destroy regional nerves, blood vessels, and fatty tissue. Envenomation by the brown recluse can lead to severe necrosis of the cutaneous tissues.1,2
In the United States, L reclusa is one of 13 species of Loxosceles—five of which have been associated with necrotic lesions resulting from bites and envenomation.3 Though rare, and virtually nonexistent across significant portions of North America,4 the brown recluse is often cited as the offending creature in reported bites involving envenomation5 (with reports sometimes outnumbering estimated numbers of specimens in a given area6). Considering the limited range within which the spider is considered endemic, any patient who presents reporting a possible brown recluse spider bite (or who presents with a wound suspected of being such a bite) must be questioned quickly and carefully. The first and foremost question: where, geographically, was the patient bitten?
Endemic Areas
Brown recluse spiders are known to be present in the subtropical areas of North America—but not in areas with high humidity. According to arachnologists in the southeastern United States, the closer one is to the Gulf of Mexico, the less likely one is to encounter a brown recluse.7 This spider is most commonly found in eastern Texas, Arkansas, areas west of the Appalachian Mountains, and northern areas of the Gulf Coast states (see Figure 18). They are virtually nonexistent along the Atlantic seaboard and the Gulf Coast,4 although lone specimens of Loxosceles species have been reported in numerous nonendemic areas, suggesting possible transport through commerce or family relocation.9 One suspected case of brown recluse envenomation was recently reported in New York State.10
If it is determined that the geographic area in question is indeed populated by brown recluse spiders, more detailed history must then be elicited from the patient regarding recent activities. The brown recluse may reside indoors and often hides in bed sheets, blankets, and stored clothing. This spider also may be found behind furniture, in basements and cupboards, or in other small, tight areas. It is commonly found in cardboard boxes stored in a closet or an attic,11 and boxes with folded flaps are a preferred dwelling place.7 (Thus, a remote chance that L reclusa can be inadvertently transported to a nonendemic area9 does exist.)
In the outdoors, the brown recluse may be found in woodpiles, piles of leaves or other natural debris, in outdoor sheds or garages, under rocks, and in other places that are relatively dark and seldom used.12
Patient Presentation/Patient History
Initially, patients with a brown recluse spider bite may present to a primary care provider with complaints of mild pain and itching, presumably around the bite site. Within eight hours, the pain becomes stabbing and penetrating and may give way to a burning sensation.7
Patients with a positive pertinent history who are at increased risk for a bite are those who live in areas where these spiders are endemic and who have been performing tasks in areas where these spiders might reside. Not wearing long pants and long-sleeved shirts contributes to the probability that a patient has sustained a bite.
Physical Examination
The site of the suspected bite and surrounding skin should be examined carefully. A pustule, generally small and white, may appear, surrounded by erythema. For as long as 24 hours following the time of the initial bite, a volcano-like lesion may be present, with a sunken central “crater” that has raised edges. While the center of the lesion is free of inflammation, the surrounding skin is typically red and inflamed.12
Pathologically, a specified sequence occurs following a bite with envenomation. Initially, platelets aggregate, followed by endothelial swelling and destruction (see Figure 2a). Gradually, this leads to the blocking of capillaries with white blood cells, which results in ischemia and ultimately necrosis.1
The clinical manifestations of the brown recluse spider bite may vary, based on the amount of venom injected and the age and overall health of the patient. One who has been bitten with minimal envenomation may experience little more than mild erythema, localized urticaria, and generalized discomfort that resolves spontaneously in three to five days.1
In patients who experience more significant envenomation, a “bull’s-eye” lesion may appear. The center of the wound may be bluish in hue, with concentric rings—an inner pale ring, and an outer reddened ring. The center of the wound subsequently forms a hemorrhagic bleb that will typically become necrotic. Eventually, as the eschar matures, the necrotic tissue will slough off, and an area of granulation will develop. Full healing of the wound may take from four weeks to as long as six months.1
Laboratory Workup
A complete blood count, including platelet count and differential, will allow the provider to observe for disseminated intravascular coagulation, hemolysis, and thrombocytopenia. The abnormal results most commonly found in patients who have sustained a brown recluse spider bite are leukocytosis and an elevated erythrocyte sedimentation rate. A skin biopsy of the site may reveal the presence of eosinophils, neutrophils, and thrombosis, all of which support the diagnosis of a brown recluse spider bite.2
A valid, reliable test to detect Loxosceles venom is needed in the clinical setting; the differential diagnosis for brown recluse spider bites is broad (see the table1,6,11,13-15 below), and diagnostic error can occur, delaying appropriate treatment for the actual presenting condition—which could be debilitating or in rare cases, fatal.16 One test for Loxosceles venom, though not currently marketed for use in humans, shows potential. It is a polyclonal enzyme-linked immunosorbent assay (ELISA) with a demonstrated ability to detect venom in rabbits for as long as seven days after injection.7 Further refinement of the polyclonal ELISA is under way in efforts to increase its sensitivity and specificity.17
Diagnosis
Diagnosis of a brown recluse spider bite is difficult at best. Other potential causes of the associated presenting symptoms should be excluded before a brown recluse spider bite is considered confirmed.
Several factors add to the difficulty of diagnosing a brown recluse bite. Oftentimes it may take the patients days or weeks after the bite to see a health care provider, and they rarely present with the spider that bit them (or that they believe bit them).1 Currently, the only true standard for proof of envenomation by a brown recluse is to collect the spider and have its identify verified by an entomologist or other expert—not necessarily the health care provider.
One condition that is frequently misdiagnosed as a brown recluse bite is methicillin-resistant Staphylococcus aureus infection (MRSA; see Figure 2b). Misdiagnosis as a bite will delay appropriate treatment for MRSA and possibly lead to transmission of infection to others, as the unaware patient does not take proper precautions to avoid spreading MRSA to others.7 Patients with MRSA who experience significant tissue eradication or tissue death, or who have developed systemic symptoms, are candidates for hospitalization and possibly surgical debridement.2
Treatment/Management
Even without proper verification that the lesion is the bite of a brown recluse, it remains essential to provide basic treatment—initially, to wash the area with mild soap and water, then elevate the affected extremity and apply ice; rest is recommended.12 The patient’s tetanus immunization status should be verified, with tetanus vaccine administered if appropriate.7,11
While most brown recluse bites will resolve without major treatment within two to three months, disabling manifestations warrant treatment. Treatment goals are to keep the skin intact, decrease the likelihood that infection will spread, and maintain circulation to the affected area.
Several treatment options are possible for a confirmed brown recluse spider bite with envenomation. Oral dapsone, initiated within 36 hours, has been shown to reduce or delay the need for surgical intervention in cases of severe necrotic arachnidism.2,13,18,19 Dosage ranges from 50 mg/d to 100 mg/d, divided bid for adults; and for children, 1.0 to 2.0 mg/kg/d, not to exceed 100 mg/d.3
Before dapsone is prescribed or administered, the patient must be tested for glucose-6-phosphate dehydrogenase (G6PD) deficiency, as dapsone use in such individuals can lead to hemolysis.3,20 Clinicians unfamiliar with this medication should request a consultation with an expert (eg, in infectious disease, wound care, pharmacology) regarding treatment and the need for monitoring potential adverse effects. Additionally, although dapsone has been recommended for this indication for longer than 20 years, few human studies have been reported to support its use.19
The anti-inflammatory effects of steroids may be useful in some cases, as they may provide red blood cell membrane–stabilizing effects in patients with systemic loxoscelism.7 Although no guideline currently exists for dosing of glucocorticoids in spider bite treatment, a shorter period of eschar duration was reported in one animal study involving methylprednisolone administered within two hours of inoculation, dosed at 2 mg/kg of body weight initially, then daily for two days longer.11
Antibiotics may minimize the inflammatory reaction at the bite site, although generally, antibiotics are reserved for infections and not recommended for prophylaxis. Antihistamines may be used to relieve minor symptoms related to histamine release (eg, itching) and also for treatment of anaphylaxis.3 Analgesics, such as acetaminophen, may be prescribed for minor discomfort. Clinicians should individualize medication use (both drug and dose) based on the needs of the patient.
Hyperbaric oxygen therapy, a modality commonly used in wound healing, has been theorized to break down sphingomyelinase-D, thus preventing further spread of venom.1,21 In patients treated with this modality for brown recluse bites, reported results have been mixed.7
Follow-Up
Daily wound checks should be performed until the lesion is noted to be improving or no longer worsening. At each follow-up for the initial 72 hours, it is recommended that patients undergo a CBC, including platelet level, to detect progression of the infection or systemic involvement, and urinalysis to check for hematuria. Renal function should be monitored as needed.1,2
Patient Education
Regarding brown recluse spider bites, patients should be advised to keep five points in mind:
• Diagnosis is made by confirmation that the spider is a brown recluse, ideally with the capture and expert evaluation of the spider22
• Workup will focus on history, geographic locale, and environ of patient when supposed bite occurred4,7,8
• Treatment varies but may include a tetanus shot, antibiotics, dapsone, steroids, hyperbaric oxygen therapy, and in severe cases of necrosis, surgery1,2,7,19,20
• Follow-up will occur routinely during the initial 72 hours1,2
• Prevention of bites includes avoiding piles of clutter in garages, sheds, and under beds; and wearing long sleeves when working in these areas.12
Finally, because the venom of the brown recluse spider is poisonous, the NIH encourages exposed persons to contact the National Poison Control Center at (800) 222-1222.23
Conclusion
Brown recluse spider bites, though most likely overdiagnosed, do occasionally occur in areas where the creature is endemic. However, a brown recluse spider bite should be considered a diagnosis of exclusion and other possibilities considered first in light of their limited presence in North America and their nonaggressive nature.
Any patient who calls to report a suspected brown recluse spider bite should be instructed to bring the spider to the office, if possible, for identification. The spider should then be identified with certainty as a brown recluse by the appropriate expert so that treatment for the patient can be based on a correct diagnosis rather than one of presumption.
The brown recluse spider (Loxosceles reclusa) is a small arachnid with great potential to inflict physical harm. More potent than a rattlesnake’s venom, the toxin emitted by the brown recluse has the ability to rupture cell membranes and destroy regional nerves, blood vessels, and fatty tissue. Envenomation by the brown recluse can lead to severe necrosis of the cutaneous tissues.1,2
In the United States, L reclusa is one of 13 species of Loxosceles—five of which have been associated with necrotic lesions resulting from bites and envenomation.3 Though rare, and virtually nonexistent across significant portions of North America,4 the brown recluse is often cited as the offending creature in reported bites involving envenomation5 (with reports sometimes outnumbering estimated numbers of specimens in a given area6). Considering the limited range within which the spider is considered endemic, any patient who presents reporting a possible brown recluse spider bite (or who presents with a wound suspected of being such a bite) must be questioned quickly and carefully. The first and foremost question: where, geographically, was the patient bitten?
Endemic Areas
Brown recluse spiders are known to be present in the subtropical areas of North America—but not in areas with high humidity. According to arachnologists in the southeastern United States, the closer one is to the Gulf of Mexico, the less likely one is to encounter a brown recluse.7 This spider is most commonly found in eastern Texas, Arkansas, areas west of the Appalachian Mountains, and northern areas of the Gulf Coast states (see Figure 18). They are virtually nonexistent along the Atlantic seaboard and the Gulf Coast,4 although lone specimens of Loxosceles species have been reported in numerous nonendemic areas, suggesting possible transport through commerce or family relocation.9 One suspected case of brown recluse envenomation was recently reported in New York State.10
If it is determined that the geographic area in question is indeed populated by brown recluse spiders, more detailed history must then be elicited from the patient regarding recent activities. The brown recluse may reside indoors and often hides in bed sheets, blankets, and stored clothing. This spider also may be found behind furniture, in basements and cupboards, or in other small, tight areas. It is commonly found in cardboard boxes stored in a closet or an attic,11 and boxes with folded flaps are a preferred dwelling place.7 (Thus, a remote chance that L reclusa can be inadvertently transported to a nonendemic area9 does exist.)
In the outdoors, the brown recluse may be found in woodpiles, piles of leaves or other natural debris, in outdoor sheds or garages, under rocks, and in other places that are relatively dark and seldom used.12
Patient Presentation/Patient History
Initially, patients with a brown recluse spider bite may present to a primary care provider with complaints of mild pain and itching, presumably around the bite site. Within eight hours, the pain becomes stabbing and penetrating and may give way to a burning sensation.7
Patients with a positive pertinent history who are at increased risk for a bite are those who live in areas where these spiders are endemic and who have been performing tasks in areas where these spiders might reside. Not wearing long pants and long-sleeved shirts contributes to the probability that a patient has sustained a bite.
Physical Examination
The site of the suspected bite and surrounding skin should be examined carefully. A pustule, generally small and white, may appear, surrounded by erythema. For as long as 24 hours following the time of the initial bite, a volcano-like lesion may be present, with a sunken central “crater” that has raised edges. While the center of the lesion is free of inflammation, the surrounding skin is typically red and inflamed.12
Pathologically, a specified sequence occurs following a bite with envenomation. Initially, platelets aggregate, followed by endothelial swelling and destruction (see Figure 2a). Gradually, this leads to the blocking of capillaries with white blood cells, which results in ischemia and ultimately necrosis.1
The clinical manifestations of the brown recluse spider bite may vary, based on the amount of venom injected and the age and overall health of the patient. One who has been bitten with minimal envenomation may experience little more than mild erythema, localized urticaria, and generalized discomfort that resolves spontaneously in three to five days.1
In patients who experience more significant envenomation, a “bull’s-eye” lesion may appear. The center of the wound may be bluish in hue, with concentric rings—an inner pale ring, and an outer reddened ring. The center of the wound subsequently forms a hemorrhagic bleb that will typically become necrotic. Eventually, as the eschar matures, the necrotic tissue will slough off, and an area of granulation will develop. Full healing of the wound may take from four weeks to as long as six months.1
Laboratory Workup
A complete blood count, including platelet count and differential, will allow the provider to observe for disseminated intravascular coagulation, hemolysis, and thrombocytopenia. The abnormal results most commonly found in patients who have sustained a brown recluse spider bite are leukocytosis and an elevated erythrocyte sedimentation rate. A skin biopsy of the site may reveal the presence of eosinophils, neutrophils, and thrombosis, all of which support the diagnosis of a brown recluse spider bite.2
A valid, reliable test to detect Loxosceles venom is needed in the clinical setting; the differential diagnosis for brown recluse spider bites is broad (see the table1,6,11,13-15 below), and diagnostic error can occur, delaying appropriate treatment for the actual presenting condition—which could be debilitating or in rare cases, fatal.16 One test for Loxosceles venom, though not currently marketed for use in humans, shows potential. It is a polyclonal enzyme-linked immunosorbent assay (ELISA) with a demonstrated ability to detect venom in rabbits for as long as seven days after injection.7 Further refinement of the polyclonal ELISA is under way in efforts to increase its sensitivity and specificity.17
Diagnosis
Diagnosis of a brown recluse spider bite is difficult at best. Other potential causes of the associated presenting symptoms should be excluded before a brown recluse spider bite is considered confirmed.
Several factors add to the difficulty of diagnosing a brown recluse bite. Oftentimes it may take the patients days or weeks after the bite to see a health care provider, and they rarely present with the spider that bit them (or that they believe bit them).1 Currently, the only true standard for proof of envenomation by a brown recluse is to collect the spider and have its identify verified by an entomologist or other expert—not necessarily the health care provider.
One condition that is frequently misdiagnosed as a brown recluse bite is methicillin-resistant Staphylococcus aureus infection (MRSA; see Figure 2b). Misdiagnosis as a bite will delay appropriate treatment for MRSA and possibly lead to transmission of infection to others, as the unaware patient does not take proper precautions to avoid spreading MRSA to others.7 Patients with MRSA who experience significant tissue eradication or tissue death, or who have developed systemic symptoms, are candidates for hospitalization and possibly surgical debridement.2
Treatment/Management
Even without proper verification that the lesion is the bite of a brown recluse, it remains essential to provide basic treatment—initially, to wash the area with mild soap and water, then elevate the affected extremity and apply ice; rest is recommended.12 The patient’s tetanus immunization status should be verified, with tetanus vaccine administered if appropriate.7,11
While most brown recluse bites will resolve without major treatment within two to three months, disabling manifestations warrant treatment. Treatment goals are to keep the skin intact, decrease the likelihood that infection will spread, and maintain circulation to the affected area.
Several treatment options are possible for a confirmed brown recluse spider bite with envenomation. Oral dapsone, initiated within 36 hours, has been shown to reduce or delay the need for surgical intervention in cases of severe necrotic arachnidism.2,13,18,19 Dosage ranges from 50 mg/d to 100 mg/d, divided bid for adults; and for children, 1.0 to 2.0 mg/kg/d, not to exceed 100 mg/d.3
Before dapsone is prescribed or administered, the patient must be tested for glucose-6-phosphate dehydrogenase (G6PD) deficiency, as dapsone use in such individuals can lead to hemolysis.3,20 Clinicians unfamiliar with this medication should request a consultation with an expert (eg, in infectious disease, wound care, pharmacology) regarding treatment and the need for monitoring potential adverse effects. Additionally, although dapsone has been recommended for this indication for longer than 20 years, few human studies have been reported to support its use.19
The anti-inflammatory effects of steroids may be useful in some cases, as they may provide red blood cell membrane–stabilizing effects in patients with systemic loxoscelism.7 Although no guideline currently exists for dosing of glucocorticoids in spider bite treatment, a shorter period of eschar duration was reported in one animal study involving methylprednisolone administered within two hours of inoculation, dosed at 2 mg/kg of body weight initially, then daily for two days longer.11
Antibiotics may minimize the inflammatory reaction at the bite site, although generally, antibiotics are reserved for infections and not recommended for prophylaxis. Antihistamines may be used to relieve minor symptoms related to histamine release (eg, itching) and also for treatment of anaphylaxis.3 Analgesics, such as acetaminophen, may be prescribed for minor discomfort. Clinicians should individualize medication use (both drug and dose) based on the needs of the patient.
Hyperbaric oxygen therapy, a modality commonly used in wound healing, has been theorized to break down sphingomyelinase-D, thus preventing further spread of venom.1,21 In patients treated with this modality for brown recluse bites, reported results have been mixed.7
Follow-Up
Daily wound checks should be performed until the lesion is noted to be improving or no longer worsening. At each follow-up for the initial 72 hours, it is recommended that patients undergo a CBC, including platelet level, to detect progression of the infection or systemic involvement, and urinalysis to check for hematuria. Renal function should be monitored as needed.1,2
Patient Education
Regarding brown recluse spider bites, patients should be advised to keep five points in mind:
• Diagnosis is made by confirmation that the spider is a brown recluse, ideally with the capture and expert evaluation of the spider22
• Workup will focus on history, geographic locale, and environ of patient when supposed bite occurred4,7,8
• Treatment varies but may include a tetanus shot, antibiotics, dapsone, steroids, hyperbaric oxygen therapy, and in severe cases of necrosis, surgery1,2,7,19,20
• Follow-up will occur routinely during the initial 72 hours1,2
• Prevention of bites includes avoiding piles of clutter in garages, sheds, and under beds; and wearing long sleeves when working in these areas.12
Finally, because the venom of the brown recluse spider is poisonous, the NIH encourages exposed persons to contact the National Poison Control Center at (800) 222-1222.23
Conclusion
Brown recluse spider bites, though most likely overdiagnosed, do occasionally occur in areas where the creature is endemic. However, a brown recluse spider bite should be considered a diagnosis of exclusion and other possibilities considered first in light of their limited presence in North America and their nonaggressive nature.
Any patient who calls to report a suspected brown recluse spider bite should be instructed to bring the spider to the office, if possible, for identification. The spider should then be identified with certainty as a brown recluse by the appropriate expert so that treatment for the patient can be based on a correct diagnosis rather than one of presumption.
1. Wilson JR, Hagood CO Jr, Prather ID. Brown recluse spider bites: a complex problem wound. A brief review and case study. Ostomy Wound Manage. 2005;51(3):59-66.
2. Rhoads J. Epidemiology of the brown recluse spider bite. J Am Acad Nurse Pract. 2007; 19(2):79-85.
3. Arnold TC. Spider envenomation, brown recluse. http://emedicine.medscape.com/article/772295-overview. Accessed November 23, 2010.
4. Vetter RS, Hinkle NC, Ames LM. Distribution of the brown recluse spider (Araneae: Sicariidae) in Georgia with comparison to poison center reports of envenomations. J Med Entomol. 2009;46(1):15-20.
5. Pagac BB, Reiland RW, Bolesh DT, Swanson DL. Skin lesions in barracks: consider community-acquired methicillin-resistant Staphylococcus aureus infection instead of spider bites. Mil Med. 2006;171(9):830-832.
6. Frithsen IL, Vetter RS, Stocks IC. Reports of envenomation by brown recluse spiders exceed verified specimens of Loxosceles spiders in South Carolina. J Am Board Fam Med. 2007;20(5):483-488.
7. Swanson DL, Vetter RS. Loxoscelism. Clin Dermatol. 2006;24(3):213-221.
8. CDC. Necrotic arachnidism: Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep. 1996;45(21):433-436.
9. Gertsch WJ, Ennik F. The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bull Am Museum of Nat Hist. 1983;175:265-360.
10. Andersen RJ, Campoli J, Johar SK, et al. Suspected brown recluse envenomation: a case report and review of different treatment modalities. J Emerg Med. 2010 Apr 2. [Epub ahead of print]
11. Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med. 2005;352(7):700-709.
12. Nunnelee JD. Brown recluse spider bites: a case report. J Perianesth Nurs. 2006;21(1):12-15.
13. Naidu DK, Ghurani R, Salas RE, et al. Osteomyelitis of the mandibular symphysis caused by brown recluse spider bite. Eplasty. 2008 Aug 28;8:428-433.
14. Osterhoudt KC, Zaoutis T, Zorc JJ. Lyme disease masquerading as brown recluse spider bite. Ann Emerg Med. 2002;39(5):558-561.
15. Russell FE, Gertsch WJ. For those who treat spider or suspected spider bites. Toxicon. 1983;21(3):337-339.
16. Vetter RS, Bush SP. Reports of presumptive brown recluse spider bites reinforce improbably diagnosis in regions of North America where the spider is not endemic. Clin Infect Dis. 2002;35(4):442-445.
17. McGlasson DL, Green JA, Stoecker WV, et al. Duration of Loxosceles reclusa venom detection by ELISA from swabs. Clin Lab Sci. 2009;22(4):216-222.
18. Wendell RP. Brown recluse spiders: a review to help guide physicians in non-endemic areas. South Med J. 2003;96(5):486–90.
19. Rees RS, Altenbern DP, Lynch JB, King LE Jr. Brown recluse spider bites: a comparison of early surgical excision versus dapsone and delayed surgical excision. Ann Surg. 1985;202 (5):659-663.
20. Webster GF. Is topical dapsone safe in glucose-6-phosphate dehydrogenase-deficient and sulfonamide-allergic patients? J Drugs Dermatol. 2010;9(5):532-536.
21. Merchant ML, Hinton JF, Geren CR. Effect of hyperbaric oxygen on sphingomyelinase D activity of brown recluse spider (Loxosceles reclusa) venom as studied by 31P nuclear magnetic resonance spectroscopy. Am J Trop Med Hyg. 1997;56(3):335-338.
22. Bennett RG, Vetter RS. An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse or hobo spider bites in Canada. Can Fam Physician. 2004;50:1098-1101.
23. MedlinePlus, US National Library of Medicine, NIH. Brown recluse spider. www.mdconsult.com/das/patient/body/225048384-2/0/10041/32560.html. Accessed November 23, 2010.
1. Wilson JR, Hagood CO Jr, Prather ID. Brown recluse spider bites: a complex problem wound. A brief review and case study. Ostomy Wound Manage. 2005;51(3):59-66.
2. Rhoads J. Epidemiology of the brown recluse spider bite. J Am Acad Nurse Pract. 2007; 19(2):79-85.
3. Arnold TC. Spider envenomation, brown recluse. http://emedicine.medscape.com/article/772295-overview. Accessed November 23, 2010.
4. Vetter RS, Hinkle NC, Ames LM. Distribution of the brown recluse spider (Araneae: Sicariidae) in Georgia with comparison to poison center reports of envenomations. J Med Entomol. 2009;46(1):15-20.
5. Pagac BB, Reiland RW, Bolesh DT, Swanson DL. Skin lesions in barracks: consider community-acquired methicillin-resistant Staphylococcus aureus infection instead of spider bites. Mil Med. 2006;171(9):830-832.
6. Frithsen IL, Vetter RS, Stocks IC. Reports of envenomation by brown recluse spiders exceed verified specimens of Loxosceles spiders in South Carolina. J Am Board Fam Med. 2007;20(5):483-488.
7. Swanson DL, Vetter RS. Loxoscelism. Clin Dermatol. 2006;24(3):213-221.
8. CDC. Necrotic arachnidism: Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep. 1996;45(21):433-436.
9. Gertsch WJ, Ennik F. The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bull Am Museum of Nat Hist. 1983;175:265-360.
10. Andersen RJ, Campoli J, Johar SK, et al. Suspected brown recluse envenomation: a case report and review of different treatment modalities. J Emerg Med. 2010 Apr 2. [Epub ahead of print]
11. Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med. 2005;352(7):700-709.
12. Nunnelee JD. Brown recluse spider bites: a case report. J Perianesth Nurs. 2006;21(1):12-15.
13. Naidu DK, Ghurani R, Salas RE, et al. Osteomyelitis of the mandibular symphysis caused by brown recluse spider bite. Eplasty. 2008 Aug 28;8:428-433.
14. Osterhoudt KC, Zaoutis T, Zorc JJ. Lyme disease masquerading as brown recluse spider bite. Ann Emerg Med. 2002;39(5):558-561.
15. Russell FE, Gertsch WJ. For those who treat spider or suspected spider bites. Toxicon. 1983;21(3):337-339.
16. Vetter RS, Bush SP. Reports of presumptive brown recluse spider bites reinforce improbably diagnosis in regions of North America where the spider is not endemic. Clin Infect Dis. 2002;35(4):442-445.
17. McGlasson DL, Green JA, Stoecker WV, et al. Duration of Loxosceles reclusa venom detection by ELISA from swabs. Clin Lab Sci. 2009;22(4):216-222.
18. Wendell RP. Brown recluse spiders: a review to help guide physicians in non-endemic areas. South Med J. 2003;96(5):486–90.
19. Rees RS, Altenbern DP, Lynch JB, King LE Jr. Brown recluse spider bites: a comparison of early surgical excision versus dapsone and delayed surgical excision. Ann Surg. 1985;202 (5):659-663.
20. Webster GF. Is topical dapsone safe in glucose-6-phosphate dehydrogenase-deficient and sulfonamide-allergic patients? J Drugs Dermatol. 2010;9(5):532-536.
21. Merchant ML, Hinton JF, Geren CR. Effect of hyperbaric oxygen on sphingomyelinase D activity of brown recluse spider (Loxosceles reclusa) venom as studied by 31P nuclear magnetic resonance spectroscopy. Am J Trop Med Hyg. 1997;56(3):335-338.
22. Bennett RG, Vetter RS. An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse or hobo spider bites in Canada. Can Fam Physician. 2004;50:1098-1101.
23. MedlinePlus, US National Library of Medicine, NIH. Brown recluse spider. www.mdconsult.com/das/patient/body/225048384-2/0/10041/32560.html. Accessed November 23, 2010.